The present invention relates to a high yield synthesis of a tin-containing precursor for the preparation of fluorolabeled L-dopa and a L-dopa related compounds and the process for preparing that precursor and the labeled compound. More specifically, the invention relates to new alkyltin compounds (N-formyl-3,4-di-t-butoxycarbonyloxy-6-(trimethylstannyl)-L-phenylalanine ethyl ester and related compounds), its preparation and the production of 6- .sup.18 F!fluoro-L-dopa by reaction with three different cyclotron-produced F-18 labeled fluorinating agents (F.sub.2, acetyl hypofluorite, and OF.sub.2).
Several different methods have been disclosed in the literature for preparing fluorine labeled L-dopa. However, they are all time consuming, require numerous processing steps to produce pure product and result in low to modest yields.
The labeled L-dopa compound is radioactive and as a result has a limited lifetime. Also, because of the radioactivity of the material, it is desired that the handling and processing of the material be kept to a minimum and that the yield of the desired isomer be as high as possible to eliminate the need to produce several batches of the 6-isomer to meet daily laboratory needs.
Thus, there is a need for a shelf stable precursor. Further, there is a need for a high yielding process which can be performed in a short period of time.